Analysis of water distribution in delipidated human hair by small-angle neutron scattering (SANS)

It is known that damaged hair has a part of its internal structure damaged, and its water absorption and desorption behavior are different. In recent years, it has been reported that internal lipids play an important role in the adsorption and desorption of water to the hair. Therefore, we investigate whether the water distribution in hair and the amount of internal lipids are related.

To investigate the effect of internal lipid on water distribution, we prepare human hair samples with and without a partial lack of internal lipids. Internal lipids have been removed using formic acid. The distribution of D₂ O in the hair is investigated using small angle neutron scattering (SANS) under the wet and dry conditions of each hair sample.

It is found from the obtained SANS data that formic acid-treated hairs tended to have fewer 40Å-sized water clusters that were periodically present along the fibre axis in the wet condition. On the other hand, in the dry condition, there were no differences in water distribution between samples.

These observations are believed to have been caused by the reduction of 40Å-sized water clusters existing on the constituents removed by formic acid treatment, especially the hydrophobic (lipid) constituent tissues. Consequently, it is clarified that internal lipids are deeply involved in the state of water distribution on hair in wet conditions.